This invention relates generally to a hold down assembly for a printing press die and particularly to a quick release hold down assembly which facilitates the rapid release and replacement of the die.
Web fed printing press dies which have on their surface engraved patterns are placed in contact with a hardened anvil cylinder with the web therebetween and the die requires a hold down unit to maintain contact between the die and the anvil cylinder. When a job is completed and a new job commenced it is necessary to replace the die and substitute it with a die of the same general characteristics but with a different engraved surface pattern.
In general, conventional hold down assemblies include adjusting screws for pressure adjustment of the die to insure that proper cutting pressure is achieved. Traditionally, die hold down assemblies for relatively wide web presses have been bulky and heavy and, in consequence, difficult to handle. Although lighter weight units have been provided for narrower web presses, both heavy and lightweight units have required considerable machining and have required cumbersome attachment to the press, usually by bolting. Invariably, the die pressure adjustment has utilized long threaded screws to provide adjustment for a wide range of die sizes at different die stations.
In consequence of the use of this type of hold down assembly, die replacement has been very time-consuming resulting in considerable downtime particularly in the case of short run jobs in which removal and replacement of dies may be required several times daily involving unbolting and rebolting of the unit and readjustment of the screw adjustment where a different size die is required.
In addition to the above problems, the use of one piece hold down assemblies, that is units spanning between the sides of the press, a further problem in that the size and configuration of the hold down assembly often prevents the operator from having a clear view of the web and interferes with trim removal.
The present hold down unit solves these and other problems in a manner not revealed by the known prior art.